Optical fiber cables (herein “cables”) are ubiquitous in data and telecommunications. A typical cable comprises an optical fiber encased by a buffer, which protects the fiber and provides strength to the cable. The diameter of a buffered fiber typically ranges from 250 to 900 μm depending upon the application. Cables are also frequently jacketed in which aramide strength members surround the buffer and are encased in a protective polymeric sheathing. These cables, both jacketed and non-jacketed, form the backbone of essentially all optical communications.
Frequently, cables must be connected together to effect an optical coupling between them. This connection is performed using a splice. Although splices are common and well known in the art, Applicants have identified a number of properties that splices should possess, but few do.
First, a splice must hold the cables such the fibers are in optical alignment. This requires aligning the core of one fiber with the core of the other. Considering that cores for multimode fibers are only 50/62.5 μm, and those for single mode fibers are even smaller at 8/10 μm, tolerances for radial offset can be as low as 1 μm. Thus, extremely accurate and precise positioning of the fibers is necessary to achieve suitable optical coupling.
Second, since different cables must be connected in networks in the field, a splice should be field installable, meaning a technician should be able to use relatively simple tools to optically couple the fibers in a simple and reliable way.
Third, the splice must be durable and resilient to common environmental assaults such as dirt and debris. If dirt or other debris is able to penetrate the housing, it can wreak havoc with the mechanism that effects the splice or even degrade the optical performance of the splice.
Fourth, the splice should be structurally robust and resist pulling forces on the cables it joins. To this end, Applicants have recognized that transferring the axial forces on the cable to a load bearing component of the splice and away from the clamping mechanism of the splice provides for the most robust design. Transferring these forces to a load bearing component is particularly important with respect to jacketed fibers. That is, the splice should be capable of accommodating jacketed fibers and exploiting the strength members that they contain by securing these strength members to the load bearing component of the splice.
Fifth, a splice should exploit certain standards and commonality among other optical components to make it universal. For example, since a splice should be field installable, it would be preferable that the splice use fiber termination mechanisms that are already in use in field-installable connectors. In addition to using similar mechanisms and tools as used in the connector field, the splice should also interengage within closures with known and commercially available holders such as those manufactured by Richco.
Sixth, the splice should be capable of coupling fibers independent of the buffer or coating diameter. That is, the splice should be capable of splicing fibers having buffer diameters ranging from 250 to 900 μm, which are common in the industry.
Although the prior art offers splices which provide some of these features, none provide all. For example, one common approach is a fused splice in which the optical fibers are fused together using an energy source such as a laser, electric arc, or gas flames to heat the fiber ends. Although such a design is advantageous from the standpoint of optical alignment and usually results in an optical coupling having a low insertion loss, it requires specialized equipment and does not exploit techniques and tools already in use for terminating connectors, thereby diminishing its versatility.
Another prior art approach to splicing is the use of a clam-shell type splice as used, for example, in the CoreLink product line (offered by Tyco Electronics, Harrisburg, Pa.). In this design, two halves of a splice are urged together by resilient means such as a spring member. To effect the splice, a tool is inserted into the splice to wedge or cam the two halves apart to allow the fibers to be inserted. When the fibers are in place, the camming or wedging tool in removed and the splice halves clamp shut by virtue of the resilient means. Although this splice design has been effective in the past and provides for adequate optical alignment and simple field installation, it is not particularly durable. That is, there is a seam along its length, which is susceptible to dirt and other debris. Furthermore, axial loads on the cable are transmitted directly through the optical splice, rather than be transferred to a separate load-carrying component. Furthermore, the splice tends to be an unusual shape (typically an elongated rectilinear shape), and consequently does not interengage with standard holders. Finally, the clamping mechanism it uses is unique and not used in field installable connectors, thus, the tooling required for this splice is unique to this splice.
Yet another splice involves rotational actuation and is offered by Corning. Specifically, this splice involves one component rotating relative to another to cam down on a fiber joint and hold the fibers together. Although this device is advantageous from the standpoint of its field installability, the fiber alignment may suffer. Specifically, since the rotational actuation involves asymmetric radial pressure on the fibers within, a certain degree of fiber dislocation may occur during actuation. Furthermore, this design is not particularly durable. Specifically, to accommodate the rotational actuation, the housing is split and has annular seam. Such a seam is susceptible to dirt and other debris. Furthermore, this design is susceptible to axial loads translated through the optical fibers since the loads are not transferred to a load bearing component in the splice.
Applicants have therefore identified a need for a splice that provides good fiber alignment, field installability, durability, and versatility with respect to using commercially available tools and splice accessories. The present invention fulfills this need among others.